Final answer:
The correct answer to whether ozone in the upper atmosphere is poisonous to life is b. False. Ozone in the upper atmosphere is not only non-toxic but is essential for life on Earth as it absorbs harmful UV radiation. Ground-level ozone, however, is harmful and a major component of smog.
Step-by-step explanation:
The question asks whether ozone in the upper atmosphere is poisonous to life, and the correct option is b. False. Ozone at ground level, where it is a component of smog, is indeed harmful to life. However, ozone found in the upper atmosphere, particularly in the stratosphere, is crucial for life on Earth. This ozone forms a layer that absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, which, if it reached the Earth's surface in full intensity, would cause severe cellular damage to living organisms and disrupt the biosphere.
The upper atmospheric ozone performs several critical functions. It protects all life forms by shielding Earth from dangerous UV radiation, which can cause skin cancer in humans, harm animals, and damage plants. In addition, the ozone layer contributes to the thermal structure of the stratosphere, where its breakdown through photodissociation adds heat, reversing the temperature trend that would otherwise lead to a continually colder atmosphere as altitude increases.
It is also worth noting that while there has been concern about the depletion of this beneficial ozone layer due to pollutants like chlorofluorocarbons (CFCs), international agreements have successfully capped and reversed some of the damage, exemplifying global cooperation in maintaining Earth's habitability.